Antibody-mediated bacterial adhesion to cytomegalovirus-induced Fc receptors. Potential relationship to secondary infections complicating herpesvirus infections.

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Abstract

Cytomegalovirus (CMV) and other viruses within the herpes group have recently been shown to induce Fc receptors in infected monolayers. We have examined the possibility that such receptors might facilitate the adherence of antibody-coated bacteria to CMV-infected cells. To do this, we infected confluent human embryonic lung (HEL) cell monolayers with CMV (strain AD 169) and then used a double radiolabel assay to measure adherence of Escherichia coli 06 to both infected and control monolayers. We examined infected monolayers 48 h after viral seeding, at which time 30-60% of the cells exhibited characteristic cytopathic changes. We compared the adherence of untreated E. coli 06 with the adherence of E. coli 06 that had been preincubated for 1 h at 37 degrees C with either nonimmune or anti-E. coli 06 antiserum. Pretreatment of the E. coli 06 with specific antiserum significantly enhanced its adherence to CMV-infected, but not to control, monolayers (P less than 0.01 by the Mann-Whitney U test). We did not see such enhancement when we used anti-E. coli 06 antiserum to treat a nontypable E. coli. The augmented adherence of antibody-coated E. coli 06 to CMV-infected monolayers was abrogated by pretreating the monolayers with nonimmune serum or purified Fc fragments, but not by pretreating with IgA, IgM, or 1 mM trypan blue. Preincubating HEL cell monolayers with 100 U/ml human leukocyte interferon for 72 h at 37 degrees C did not affect the adherence of antibody-coated E. coli 06 to the monolayers. To determine if antibody-coated bacteria that adhered to the surface of CMV-infected monolayers might themselves act as receptors for microorganisms with Fc binding potential, we compared the adherence of Cowan strain Staphylococcus aureus to CMV-infected and control monolayers that had been preincubated with antibody-coated E. coli 06. The S. aureus adhered significantly better to the former monolayers (P less than 0.001). These results illustrate a previously unrecognized mechanism by which certain herpesviruses might enhance the adherence of secondary pathogens to nonphagocytic cell populations. Such a mechanism, if active in vivo, might facilitate the colonization of mucosal surfaces by these pathogenic microorganisms, and in this way might contribute to both the reported predisposition of CMV-infected patients to secondary infections and to the high prevalence of S. aureus in the vaginal flora of women with histories of genital herpes.

Authors

P A Mackowiak, M Marling-Cason, J W Smith, J P Luby